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820-3437B doesn't turn on

Bouba148

Bouba148

New member
Water Damaged

ppbus_g3h: 8.19V
pp3V42: 3.431V
PPVRTC_G3H: 3.430V

L5001 corroded and bad ( no PP3V3_S5_SMC_VDDA)
Replaced L5001: PP3V3_S5_SMC_VDDA: 3.431V

PP5V_S5: 0V
pp3V_S5: 0V

@U7501:
S5_PWR_EN:0V
P5VS4RS3_EN: 0V


SMC_PM_G2_EN: 0V
SYS_ONEWIRE: 3.409V
SMC_RESET_L: 3.400V
PP3V3_S5_AVREF_SMC: 3.298V
PM_BATLOW_L: 0.017V
SMC_ADAPTER_EN: 0V

SMC_TCK: 3.430V
SMC_TMS: 3.430V
SMC_TDO: 3.430V
SMC_TDI: 3430V

Reheat SMC: NOK
if PPBUS 8.19V so SMC is not talking to U7100 right?

Next Step Rebal SMC?
 
Bouba148

Bouba148

New member
Hi 2Informaticos,

Just reballed the SMC and I have almost the same readings: In green the voltages which were 0V before and changed:

ppbus_g3h: 8.19V
pp3V42: 3.428V
PPVRTC_G3H: 3.428V

PP5V_S5: 0V
pp3V3_S5: 0.230V

@U7501:
S5_PWR_EN:0V
P5VS4RS3_EN: 0V


SMC_PM_G2_EN: 0V
SYS_ONEWIRE: 3.408V
SMC_RESET_L: 3.397V
PP3V3_S5_AVREF_SMC: 3.298V
PM_BATLOW_L: 0.223V
SMC_ADAPTER_EN: 0V

SMC_TCK: 3.427V
SMC_TMS: 3.427V
SMC_TDO: 3.427V
SMC_TDI: 3427V

Also when I took out the SMC, 4 pads where missing on the board, 1 was gnd and the 3 others are some NC nets (named NO_TEST Nets in the schematic )
No sure they are used, NC stands for Not Connected no?
 
Last edited:
Bouba148

Bouba148

New member
Replaced SMC from the same exact board:

PP5V_S5: 5.049V
pp3V3_S5: 3.354V
PP5V_S4RS3: 0V
P5VS4RS3_EN: 0V
S4_PWR_EN: 0v
PM_SLP_S5_L: 0v
PM_BATLOW_L: 3.349V
SMC_PM_G2_EN: 2.34V
SMC_ADAPTER_EN: 0V
SMC_ONOFF_L: 3.429
SMC_BC_ACOK: 3.211V

The SMC_SYS_KBDLED pad is missing on the board but this one is only used for the keyboard backlight and is attached to U7750, I'm also very surprised that this chip (U7750) is noted as CRITICAL.
Why the keyboard backlight would be critical and preventin g the board to Start........Hummmm?
 
2informaticos

2informaticos

Administrator
Staff member
CRITICAL for its function on the machine, not for general...

SMC_ADAPTER_EN is not correct yet.
Are you using original 60/85W Magsafe 2 charger?
Be sure SMC is properly soldered.
SMC_PM_G2_EN is also lower than expected.
These two things make me doubt about SMC, or its solders...
 
Bouba148

Bouba148

New member
H 2Informaticos,

Yes I know that thoses to voltages are not ok that's why I've put them in bold.
Yes I'm using either official 85W charger or Lab Power supply with 2 officials cords attached to it: magesafe1 and 2 and both in 85W.
I'm affraid that if I remove that smc again for reballing it will fragilize it.
 
2informaticos

2informaticos

Administrator
Staff member
Don't reball it.
Put good flux and reheat.
Be sure to melt the balls and gently tap it, to see it "dancing" a bit...
If still same issue, try other SMC.
 
Bouba148

Bouba148

New member
I did all that but now I've lost the S5 rails now.
I think that SMC is now good for the trash.......and I don't have anymore of that board.
I think I'll just re-assemble the mba to give it back to it's owner because of the tme passed on it I'm not profitable at all.
As usual thanks for your support.
 
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